Stable alkaline detergents



United States Patent 3,382,178 STABLE ALKALINE DETERGENTS Kenneth J.Lissant and Frederick J. Ludwig, Sr., St. Louis, Mo., assignors toPetrolite Corporation, Wilmington, DeL, a corporation of Delaware NoDrawing. Filed Feb. 1, 1965, Ser. No. 429,639 1 Ciaim. (Cl. 252135)ABSTRACT OF THE DISCLOSURE Stable alkaline detergent compositions foruse in machine dishwashing, machine bottle washing and in generalpurpose heavy duty cleaners including inorganic alkali metal detergentsalts selected from the group consisting of alkali metal carbonates,alkali metal borates, alkali metal polyphospates, alkali metalhydroxides, alkali metal silicates, and mixtures thereof, in combinationwith (1) defoaming nonionic surfactants such as oxyalkylated compoundsof the general formuia Z[(OA),,OH] where in Z is the oxyalkylatablematerial, A is the radical derived from the alkylene oxide, which canbe, for example, ethylene, propylene, butylene oxide, etc., and thelike, n is a number determined by the moles of alkylene oxide reacted,for example to 2000 or more and z is a whole number determined by thenumber of reactive oxyalkylatable groups, and (2) a small but effectiveamount of antioxidant etfective to reduce, inhibit and/or prevent thedegradation of the nonionic surfactant thereby rendering the nonionicsurfactant stable in the stable alkaline detergents.

This application is copending with application Ser. No. 429,620, filedon Feb. 1, 1965, now US. Patent No. 3,356,612 and this application andsaid copending application have a common assignee.

This invention relates to stable detergents, including stable detergentcompositions for use in machines dishwashing, machine bottle washing andin general purpose heavy duty cleaners.

Machine dishwas'hing is used in connection with practically allcommercial and institutional dining facilities as Well as in a rapidlyincreasing proportion of private homes. In commercial machines, thedishes to be washed are introduced into a zone where detergent solutionis sprayed over them, the detergent solution :being recycled and usedrepeatedly and fortified and replenished intermittently. In homemachines the detergent is used for only one load of dishes and is thendiscarded although it too is recirculated during the washing operation.Hence in both types of machines, food soil concentrations in the washsolution of 0.05 to 0.1% or higher are considered to be moderate underaverage conditions.

It has been the practice in formulating machine dishwashing detergentsto use in the main various combinations of inorganic sodium andpotassium salts, such as polyphosphates, silicates, carbonates and basicmaterials such as sodium and potassium hydroxides. It has not beenpossible to use effective amounts of well-known organic detergents suchas the alkyl aryl sulfonates, alkyl sulfonates, alkanol amides or alkylaryl polyethers in spraytype mechanical dishwashing detergents becauseof the foam these detergents develop during the washing operation. Thisfoam causes over-flow and loss of the wash solution, impairs themechanical operation of the machine, and lowers the pressure at whichthe washing fluid is impelled against the utensils to be cleaned. Thein0rganic materials themselves do not foam and, at low concentrations offood soil (less than 0.01%), perform satisfactorily in mechanicaldishwashers. However, with increases in food soil concentration togreater than about 0.03%, foaming becomes a serious problem even withthe use of purely inorganic detergent system. This is because theinorganic detergent systems, being alkaline, can cause somesaponification of fatty food soils. This, plus the natural foamingproperties of protein food soils, tends to produce foam in the washtank.

Recently, certain low foaming, organic, non-ionic detergents have beenmade available commercially which can be incorporated in small amountswith inorganic materials in mechanical dishwashing formulations withoutseriously increasing their foaming tendency. These materials addsomewhat to the detergency efficiency of the compound formulation. Inaddition, compounds of this type have been found to have pronouncedeffect of inhibiting foam where heavy food soil loads are present, or inmaintaining internal Wash pressure at a high level under theseconditions.

Wash pressure is defined herein as the pressure registercd on amanometer or pressure gauge by a Pitot tube set at the outlet of thewash nozzle. The force of the wash spray against a dish surface isdirectly proportional to this wash pressure. Since it has been shownthat the wash action of the wash spray contributes most to gross soilremoval, maintenance of the original wash pressure built into themachine is very important.

Excessive foaming in machine dishwas-hing has long been a recognizedproblem; and, although billowing foam is an obvious indication oftrouble, a real wash pressure problem may exist even without thisobvious symptom. For example, an aerated wash solution, though not soeasily detected, may be as serious a problem from the standpoint ofwashing eificiency as billowing foam. An aerated wash solution, as usedherein, is defined as a liquid with many small air occlusions or bubblesdispersed in it as contrasted with foam which, as used herein, isdefined as a colloidal dispersion of air in liquid floating on top ofthe wash solution.

Conventional machine dishwashing detergent systems originally were dry,inorganic systems and consisted entirely of mixtures of alkaline salts.The detergent system is required to perform three essential functions:(1) soften the water so that the detersive action can take place moreeffectively; (2) remove the soil from the dishes thoroughly, completelyand rapidly; and (3) leave the dish surface in a state where the waterdrains in a continuous film without breaking into little hanging dropsor streams. Many of the alkaline salts act as both water softeners andsoil removers but will be discussed on the basis of their primaryfunction.

Sodium carbonate, although it is among the least effectivewater-softening agents, together with its sesquicarbonate, is almostuniversally used as a component in dishwashing compounds, because of itslow cost. The detergent compositions of this invention can contain from099% by weight sodium or potassium carbonate.

The best and most efficient water-softening ingredients are thecondensed polyphosphates, including the tripolyphosphates and thepyrophosphates. The detergent cornpositions of this invention cancontain from O70% by weight sodium or potassium polyphosphates.Othersequestering agents, including organic materials such asethylenediamine-tetracetic acid and sodium gluconate, can also beemployed in compositions of this invention, particularly in formulationsfor dairy use containing high percentages of caustic.

Polyphosphates have been shown to promote corrosion of certain metalparts of dishwashing machines but this corrosive effect can be overcomeby including a relatively large proportion of a silicate in thecomposition. In this connection, metasilicate is important, not onlyfrom the standpoint of the machine itself, but also from the standpointof the utensils washed. For instance, regardless of whetherpolyphosphate is present in a solution or not, highly alkalinedishwashing detergents containing no silicates can attack, etch, anddarken aluminum utensils. Some of these formulations also have adestructive action on the over-the-glaze dish patterns. Suitableproportions of silicates in the formulation help overcome thesedifficulties.

The soil-removing ingredients commonly employed in dishwashing compoundsinclude borates and carbonates, which are relatively ineffective, andorthophosphates and metasilicates, both of which are highly effective.The detergent compositions of this invention can include 70% by weightof trisodium or tripotassium phosphate and 050% by weight of sodium orpotassium metasilicate.

More recently small amounts of synthetic organic surfactants or Wettingagents have been incorporated into machine dishwashing formulations topromote smooth drainage drying, i.e., to prevent water break. Someformulations include from 1% to 5% or more of a low foaming,polyethenoxy type nonionic surfactant. The detergent compositions ofthis invention can include 050% by weight of such synthetic, organic,low foaming polyethenoxy type nonionic surfactants.

Conventional machine dishwashing compositions employed for glass andbottle washing normally contain caustic soda as the major cleaningingredient. Alkalies tend to attack glass surfaces but this can beinhibited by zincates, beryllates, or aluminates. As stated above,sodium gluconate and ethylenediaminetetracetic acid can be used assequestering agents for high caustic content solutions. The detergentcompositions of this invention can include 43-99% sodium or potassiumhydroxide.

Hence the conventional detergent systems into which the polyoxyalkyleneglycol mixture is incorporated contain as the principal detersive agentwidely varying proportions of sodium or potassium polyphosphates, i.e.,0.70%, sodium or potassium silicates, i.e., 050%, sodium or potassiumcarbonates, i.e., 2-99%, sodium or potassium hydroxides, i.e., 0-100%and trisodium or tripotassium phosphates, i.e., O-70%. The amount of thepolyoxyalkylene glycol mixture ordinarily constitutes about 0.5 to byweight of the final deter-gent composition.

In addition to using highly alkaline compositions containing sodiumhydroxide in bottle washing compositions, similar types of alkalinecompositions also are employed in the cleaning of stainless steelequipment, utensils and piping which are used in all types of foodprocessing industries (such as milk products, bakery products andvarious protene concentrates) and related industries, for example wherematerials such as glues are used. The washing operations usuallyinvolves spraying, vigorous agitation, or vigorous recirculation orcombinations thereof; and as a result considerable foaming develops.Controlling foam in these applications is important toward achievingthorough cleaning.

The duration of storage for dishwashing compositions, bottle washingcompositions and metal cleaning compositions, before they are used, maybe three to six months or even longer. Therefore, the defoamingsurfactants must be protected during this time against degradation bythe alkaline constituents in the composition to assure the consumer thatan adequate amount of defoaming agent is present at the time of washingthe equipment, utensils and piping in order for the foam to becontrolled effectively.

This problem of formulating machine dishwashing compositions, bottlewashing compositions and metal-washing compositions and the like iscomplicated by the fact that nonionics are degraded by alkalineconstituents of the formulations.

Stated another way, oxyalkylated compounds of the nonionic type areunstable in the presence of alkaline materials. When nonionics of thistype are employed in alkaline compositions, they tend to degrade uponstorage. Thus, alkaline compositions do not have sufficient shelf-lifeto yield completely satisfactory products. For example, when certaindefoaming nonionic detergents are employed and formulated in alkalinecompositions, they tend to degrade and result in losing their ability todefoam; and as a result, the alkaline composition becomes unsatisfactorybecause the amount of defoarning surfactant remaining is unable tocontrol the natural foaming tendency which develops when proteinaccoussoil is in contact with the alkaline constituents. This increase infoaming is extremely detrimental to machine operations. For example, indishwashing machines foam prevents pumps and sprays from operatingproperly and heavy duty metal cleaners from cleaning thoroughly.

We have now discovered that, when nonionics are employed in conjunctionwith an antioxidant, the degradation of nonionics in such alkalinecompositions can be reduced, inhibited and/ or prevented. Stated anotherway, the nonionics are rendered much more stable in alkaline systemswhen in contact with an antioxidant. For example during storagedegradation of the nonionic is greatly minimized by incorporating anantioxidant in the system. This invention is applicable to allformulations in which alkaline materials are employed with nonionics.

A small but effective amount of antioxidant is employed in thisinvention, i.e., effective in reducing, inhibiting and/or preventing thedegradation of nonionics.

Since a wide variety of nonionics and antioxidants and other componentscan be employed in the detergent system, the effective amount ofantioxidant will vary widely. In practice we employ one or moreantioxidants in at least about 0.01% by weight such as from about 0.1 to10.0%, for example from about 0.3 to 5.0%, but preferably from about 0.5to 2.0% based on weight of the nonionic surfactant in the formulation.

In general, the nonionic employed in the formulation is less than about5% by weight of the total formulation, but more can be employed ifdesired.

A wide variety of nonionics can be employed in this invention. Ingeneral, the nonionics employed are oxyalkylatcd compounds of thegeneral formula wherein Z is the oxyalkylatable material, A is theradical derived from the alkylene oxide which can be, for example,ethylene, propylene, butylene oxide, etc, and the like, 22 is a numberdetermined by the moles of alkylene oxide reacted, for example 10 to2000 or more and z is a whole number determined by the number ofreactive oxyalkylatable groups. Where only one group is oxyalkylatableas in the case of a substituted or unsubstituted monofunctional phenol,a straight chain biodegradable alcohol, or a branched-chain alcohol,then z=1. It is known that normal alcohols are biodegradablesuch as,those obtained by saponification of natural waxes such as sperm oil,those obtained by reduction of fatty acids derived from coconut oil,palm kernel oil, or tallow and those obtained from petroleum sources,such as for example, the mixtures of C through C straigh -chain primaryalcohols now commercially available from Con tinental Oil Co. Where Z iswater, or a glycol, z=2. Where Z is glycerol, z=3, etc.

As is well known, alkylene oxides can be reacted with variousoxyalkylatable materials (i.e. materials which contain hydrogen atomscapable of reacting with a 1,2- alkylene oxide) to form polyalkyleneoxide derivatives thereof. Thus, where an oxyalkylatable material of theformula ZH is reacted with an alkylene oxide such as ethylene oxide,there is obtained a compound of the formula where n is a numberdetermined by the moles of alkylene oxide reacted and z is a numberdetermined by the compounds oxyalkylatable hydrogens.

Many polyalkylene oxide block polymers have been prepared containingdefinite homogeneous block units or segments of ethylene oxide,propylene oxide, butylene oxide, etc., such as disclosed in U.S.P.2,674,619, 2,677, 700 and elsewhere.

Where ethylene oxide is reacted with water, a polymeric polyethyleneglycol of the type is formed. Similarly, where propylene oxide isreacted with water, a polymeric polypropylene glycol of the type H(OPr)O(PrO) H is formed. When water is first reacted with ethylene oxidefollowed by reaction with propylene oxide, a polymer containing blocksof ethylene oxide units and blocks of propylene oxide are formed,H(OPr). (OEt) O(EtO) (PrO) I-I, or when added in the reverse order thefollowing block polymer is formed:

Block polymers of this type can be formed by adding infinite numbers ofblock units, for example This block-wise or sequential addition could becontinued infinitely. Since only two types of alkylene oxides areemployed, these polymers are (ii-block polymers.

Where three or more different types of alkylene oxides are employed,ter-block polymers are formed as illustrated by sequentially addingethylene oxide, propylene oxides, and butylene oxides to water to form:

These tor-block units may also be continued infinitely. Where, forexample, other alkylene oxides are used in addition to ethylene,propylene, and butylene oxides, a higher type of block polymer isformed, such as when octylene oxide or styrene oxide are additionallyreacted. It is to be noted the block units of these polymers withinthemselves are homogeneous units, i.e., each block is derived from asingle alkylene oxide.

Polyalkylene oxides have also been prepared by reacting mixtures ofalkylene oxide such as when a mixture of ethylene oxide and propyleneoxide are reacted. When this is done, a random of hetero-polymer isobtained. Thus, for example, where a 50/50 molar mixture of EtO and PrOare reacted with an oxyalkylatable material, such as water, one obtainsa polymer having no orderly arrangement of the alkylene oxide unitssince the distribution of EtO and P units in the molecule is random maybe designated by Carbide & Carbon sells these mixed glycols under theUcon trademark.

MO as employed herein refers to mixtures of ethylene oxide inconjunction with a hydrophobic alkylene oxide, i.e., an alkylene oxidehaving more than two carbon atoms. Thus, the hydrophobic alkylene oxidesinclude propylene oxide, butylene oxide, amylene oxide, octylene oxide,styrene oxide, methylstyrene oxide, cyclohexene oxide, etc. However, inpractice we prefer to employ ethylene oxide in conjunction withpropylene and/ or butylene oxide.

The alkylene oxides employed herein are 1,2-alkylene oxides of theformula wherein R R R and R are selected from the group consisting ofhydrogen, an aliphatic, cycloaliphatic, aryl, etc. group for exampleethylene oxide, propylene oxide, butylene oxide, amylene oxide, octyleneoxide, styrene oxide, methylstyrene oxide, cyclohexene oxide, (where Rand R are joined to make a ring), etc.

Equivalents of alkylene oxides can also be employed, for examplealkylene carbonates, i.e. ethylene carbonate, propylene carbonate,butylene carbonate, etc. In addition, alkylene oxides of the glycide,methyl glycide type can also be employed.

Since the products of this invention are preferably block polymerscontaining blocks or segments of alk lene oxide units which are addedsequentially, the reaction is in essence a stepwise procedure. For thesake of simplicity of presentation, the invention will be illustrated byemploying as a base oxyalkylatable compound ZI-I and by employing onlyethylene, propylene, and butylene oxides with the understanding thatother hydrophobe oxides can be used in place of propylene and butyleneoxides such as amylene oxide, octylene oxide, styrene oxide, etc. Theseare shown in the following table.

The products formed are represented by means of a statistical formulaand are often referred to as cogeneric mixtures. This is for the reasonthat if one selects any oxyalkylatable material and subjects it tooxyalkylation, particularly where the amount of oxide added iscomparatively large, for example 30 units of EtO, it is well known thatone does not obtain a single constituent such as RO(C H O) H. Insteadone obtains a cogeneric mixture of closely related homologous compoundsin which the formula may be shown as the following: RO(C H O),,H where Xas far as the statistical average goes, is 30, but the individualmembers present insignificant amounts may vary from compounds where xhas a value of 25 and perhaps less to a point where x may represent 35or more (see Flory Chemical Reviews, vol. 30, No. 1, page 137). Thus,the formulae presented herein are statistical formulae.

TABLE 1 Step I zruno m )n 1z Z[(Buo),,H Z[(MO),,H],, Z[(Pro rxuo),,rr

Step 11 Reaction of the Step I product with one of the five oxides ormixtures employed in Step I, which oxide had not been reacted in theimmediately preceding step. For example:

Step IV involves the oxyalkylation of the products of Step III. Step Vinvolves the oxyalkylation of Step IV. Further oxyalxylations involveSteps VI-X or higher. This process can be continued ad infinitum.

Where Z is derived from ZH which is H O, 2:2. Where Z is derived fromZAH, Z is the moiety of an alcohol or a phenol and 2:1. Where Z isderived from a polyol such as glycerol, z 2. Examples of ZOH include thefollowing:

(1) Oxyalkylatable monofunctional compounds such as alcohols of the C HOH series for example methanol, propanol, butanol, pentanol, hexanol,octanol, nonanol, decanol, undecanol, dodecanol, tridecanol,tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, etc.(2) Corresponding unsaturated alcohols, for example oleyl, linoleylalcohols, (3) phenolic compounds ineluding those of the general formulaWhere R is hydrogen or a substituted group for example those of the C Hseries, i.e. methyl, ethyl, propyl, butyl, etc., correspondingunsaturated radicals: phenyl, substituted phenyl, etc., and m is aninteger for Examples 13, but preferably 1.

In addition condensed ring aromatic compounds can be employed, forexample, naphthol, substituted naphthol, etc.

Polyols can also be employed as exemplified by the following:

Polyhydric alcohols Ethylene glycol Propylene glycol Diethylene glycolTrimethylene glycol 2,3-3utanediol l,4-r'iihydroxy-2-butene1,12-dihydroxy octadecane 9 1,4-dihydroxy cyclohexane2,2-dimethyl-1,3-propanediol 2-ethyl-2-butyl propanediol-1,3 GlycerolEryth-ritol Sorbitol Mannitol Inositol Trimethylol propanePentaerythritol Polyallyl alcohol Bis (4-hydroxycyclohexyl) dimethylmethane 1,4-dimethylol benzene 4,4'-dimethylol diphenyl Dimethylolxylenes Dimethylol naphthalenes, etc.

Beta hydroxyethyl ethers of glycerol, pentaerythritol,

" sorbitol, mannitol, etc.

Condensates of alkylene oxides such as ethylene oxide; propylene oxides;butylene oxide; isobutylene oxide; glycidol; glycid ethers, etc. withpolyhydric alcohols such as the foregoing.

Polyhyd-ric phenols Hyd-roquinone Resorcinol Pyrogallol Bisphenol(predominantly 4,4'-dihydroxy diphenyl dimethyl methane) Dihydroxydiaryl sulfones Phenol-aldehyde resins (See US. Patent 2,499,365)

The molecular weight of the nonionics of this invention can vary widelyfrom such as 500 to 100,000, or higher, for example a range of 1,000 to25,000, preferably 1,500- 7,000 with an optimum of 2,0005,000. However,the specific preferred and optimum molecular weight will vary with eachparticular application.

The moles of alkylene oxide on each block unit can also vary widely,such as from 520() moles, or more, of alkylene oxide, for example, arange of 150 moles with an optimum of -60 moles per block unit. However,the range of the specific preferred block unit will vary with thespecific surfactant molecule and with the system in which the surfactantis employed.

In general the nonionics which are most effective in the practice ofthis invention are those which contain more than one kind of alkyleneoxide, either in random distribution, in block formation or both. Wherethe nonionic is a block polymer, it is preferred that the terminal groupbe derived from a hydrophobe alkylene oxide, i.e. one other than EtO,preferably PrO. If the terminal block is derived from ethylene oxide,then the block so derived preferably should contain less alkylene oxidemolar units than the immediately preceding hydrophobe alkylene oxideblock.

Preferably, the nonionics should be a low foaming surfactant. In useswhere biodegradability is important, it is preferable that the nonionicbe biodegradable.

One class of defoaming nonionics useful in this invention comprises apolyoxyalkylene glycol mixture consisting of a product whichstatistically represented ha a plurality of alternating hydrophobic andhydrophilic polyoxyalkylene chains or segments, the hydrophilic chains(segments) consisting of oxyethylene radicals linked one to the other,said statistically represented product having five such chains(segments) comprising three hydrophobic chains (segments) linked by twohydrophobic chains, the central hydrophobic chain (segment) constituting30% to 34% by weight of the final product, the terminal hydrophobicchains (segments) togehter constituting 31% to 39% by weight of thefinal product, the linking hydrophilic chains (segments) constituting31% to 35% by Weight of the final product, the intrinsic viscosity ofthe final product being from about 0.06 to 0.09 and the molecular weightof the final product being from about 3,000 to 5,000.

The polyoxyalkylene glycol mixture is prepared by condensing propyleneoxide with water or propylene glycol to form a polyoxypropylene glycol,condensing ethylene oxide with the resulting polyoxypropylcne glycol,and then condensing propylene oxide with the resulting oxyethylatedpolyoxypropylene glycol. The preparation must be carried out in theabove order to yield products having the required alternatinghydrophobe-hydrophile structure.

These are described in US. Patents 3,048,548 and 3,082,172 which are byreference incorporated into this application.

The compositions of this invention can also be employed as rinse agentsfor use in machine dishwashing as described in US. Patent 3,082,172.

Another class of defoaming nonionic surfactant useful in this inventioncomprises a polyoxyalkylene glycol mixture consisting of a productwhich, statistically represented, has three or more alternatinghydrophobic and hydrophilic segments. In this class of surfactant thefirst segment is hydrophobic such as that derived from a diormulti-substituted phenol, for example, a didodecyl phenol. The firsthydrophilic segment of polyoxyethylene units is attached thereto and maybe as low as weight percent of the starting hydrophobe. Then the secondhy drophobic segment (such as that derived from polyoxypropylene units)is attached thereto and may be as low as weight percent of the startinghydrophobe. In such an example, the step of alternating first with apolyoxyethylene segment and then a polyoxypropylene segment may becarried out eight times. On the other hand, where only one hydrophilicsegment of polyoxyethylene units is attached to the starting hydrophobe,the ethylene oxide employed may be as high as 460-625 weight percent ofthe starting hydrophobe and the final hydrophobic seg ment ofpolyoxypropylene units attached thereto may be as high as 675 900 Weightpercent of the starting hydrophobe.

Still another class of defoaming nonionic surfactant useful in thisinvention comprises a polyoxyalkylene glycol mixture consisting of aproduct which, statistically represented, has three or more alternatinghydrophobic and hydrophilic segments such as the first hydrophobicsegment is derived from a biodegradable straight-chain primary alcohol,for example, nC H OH. Then, the first hydrcphilic segment ofpolyoxyethylene units is attached thereto and may be as low as 94 weightpercent of the starting hydrophobe. Then the second hydrophobic segment(such as that derived from polyoxypropylene units) is attached theretoand may be as low as 200 Weight percent of the starting hydrophobe. Insuch an example, the step of alternating first with a polyoxyethylenesegment and then a polyoxypr opylene segment may be carried out at leastsix times. On the other hand, when only one hydrophilic segment ofpolyoxyethylene units is attached to the starting hydrophobe, theethylene oxide employed may be as high as 565-850 weight percent of thestarting hydrophobe and the final hydrophobic segl 1 meat ofpolyoxypropylene units attached thereto may be as high as 124048.50Weight percent of the starting hydrophobe.

A Wide variety of antioxidants including both primary or donor typeantioxidants and synergists can be employed l2 Amino compounds, such asdiarylamines and t-alkyl primary amines examples of which are: mixedalkylated diphenylamines, wnaphthylamine,

i o phenyl-ct-naphthylamine, which are capable or inhibiting, preventingor reducing phenypflmaphthyiamine, degradation of the nonionicsurfactant. The mechanism di scc butyl p pheny1ene diamine by Which thisinhibition of degradation occurs in 1'lO \:/21Y Nhsnyl-N'-cyclohexyl-p-phenylene diamine, limits the scope oi thisinvention. Heretofore published N7Nndiphanypp-phsnYlenc diaminemechanisms of antiox dant activity may or may not take 10 phenothiazineplace under the conditions or this nvention because the gpzdi d l icustomary concept about antiox dation is complicated by t d d l primaryamine, and the presence of alkaline matl'1alS AIltlOX1dE lntS of the t td l primary amine; primary and synergrst types are widely described inthe dicyciohexylamine literature and are i W965 employfzd m w andmiscellaneous antioxidants such as: stuffs, soaps and cosmetics,pharmaceuticals, essential oils, fats, petroleum, rubber and textileoils, etc. Antioxidants 3 "b1?(limethyl'z'tbutylphenyl) sulfide of thesetypes are described in Antioxidation and Antioxii dlthwcafwbonates}dants, vols. I and II by Lundherg (liiterscience Publisher, Zmc 'Pi e lsand 1962) which are by reference incorporated into the pres- 9, gua'mgmedenvalwesent application. The antioxidants permitted in foods by The fllowing table presents examples of commercial the Food and DrugAdministration are suitable for use in an iox dants which areadvantageously employed in this this invention. These include, forexample, the following invention:

TABLE II Antioxidants Commercial or Trade Supplier time 1. Food GradeAntioxidants:

1. Dilauryl tliiodipropiouate Dillydap Carlisle Chem. Wks.

2. Distearyl tliiooiprop into 3. fifi-thiodipropionic 80K 4. Butylatedhydroxy-anisole Butylated liydroxy-toluene 6. n-Propyl gallate 7.Mixtures of 4, 5 and 6 II. Animal Feed Grade: l,2-dil1ydr trimetiiylquinoline.

III. F.D.A. Approved: 2,2-mctliylene bis(4-n1ethyl-G- t-butylplienol).IV. Rubber and Gasoline Grade:

. Dicyelolicggylamiuen Mixtures of 1 and 2 PlienotlziazinePlieziotiiiazinoCuClz Polybutylatcd bisplienol V. Miscellaneous:

sation product.

primary antioxidants: gum guaiac; tocophcrols and related compounds;NDGA (nordihydroguaiaretic acid); gallio acid and the gallates (such aspropyl gallate); BHA {butylated hydroxyanisole); BHT (butylatedhydroxytoluene). Also included, for example, are the synergists:phospolipids, such as lecithin; citric acid; phosphoric acid;monoisopropyl citrate; stearyl citrate; ascorbic acid and relatedcompounds such as sodium ascorbate, isoascorbic acid, sodiumisoascorbate and ascorbyl palmitate; and thiodipropionic acid andrelated compounds such as didodecyl and dioctadecyl thiodipropionate,etc.

In addition, the primary antioxidants employed in stabilizing petroleumand rubber compositions are suitable in the invention and include: thernono-, diand trialkylphenols, alkylated bisphenols, alkylateddihydroxyaromatic compounds and amino-phenols such as, for example,

Eastman Chem. Prods. Eastman Chem. Prods. Hercules Powder.

Catalin Corp.

Eastman Chem. Prods. Grilfith Laboratory.

Disterdap B A Tenox BHT Dalpac 200. Food Grade BHT enox PG GriffithG-50.

Santoquim. Monsanto Chem. Co.

CAO 5, CA0 14 Catalin Corp.

Antioxidant 224G. American Cyanamld.

nol)

. Monsanto Chem. Co.

. Vanderbilt. Ethyl Corp.

........ Antioxidant 702 Monsanto Chem. Co. Petrolite Corp.

In addition to nonionics and antioxidants, other constituents employedin detergent compositions can be employed such as those describedherein. These include carbonates, phosphates, silicates and otheralkalinic components of dishwashing compositions.

The following examples are presented for purposes of illustration andnot of limitation. To demonstrate this invention under the extremeconditions of high alkalinity, a highly alkaline system was selected toillustrate the present invention, such as employed in cleaning ferrousmetal equipment and utensils used in the food industry. To show thestabilizing eifect of antioxidants on defoaming surfactants under highlyalkaline detergent conditions, the following formula was employed in theexamples:

Percent Sodium hydroxide 30 Defoaming surfactant 5 Sodium metasilicateanhydrous 36 Sodium carbonate 30 Total 100 The procedure to study thestabilizing effect of antioxidants on defoaming surfactants in the abovehighly alkaline detergent composition was to mix the desired amount ofsurfactant with and Without antioxidants dircctly on the NaOH component.This direct contact With NaOH presented a very extreme test for alkalinestability. Samples of this composition with the various surfactants 13to be tested were then stored in ovens to accelerate the aging process.At varying intervals samples were removed from storage and were testedin the Foam Retard Test for the defoaming ability of the defoamingsurfactant remaining after extended storage.

The detergent compositions for storage testing were prepared in thefollowing manner:

Step 1.The defoaming surfactants containing 1% antioxidant were preparedby dissolving g. antioxidant in 495 g. surfactant.

Step 2.A 2000-gram quantity of each test blend was made according to theproportions shown above, and the order of mixing was as listed. To a onegallon widemouth polyethylene jar with screw-cap lid were charged: 600g. NaOH (as small flakes) 100 g. surfactant containing either 100 g.surfactant and no antioxidant; or 99 g. surfactant and 1 g. antioxidant.

These were then mixed well with a long handled spatula.

(Step 2, continued)-700 g. granular sodium metasilicate anhydrous wasthen charged thereto and mixed well with a spatula. 600 g. sodiumcarbonate was then charged and mixed well on a roller until thoroughlyhomogeneous. Portions of this final mixture were transferred into twoone pint jars with screw-cap lids for storage in each of two ovens, onemaintained at about 175 F. and the other at about 110 F.

Step 3.The jars were removed from the respective storage temperaturesfrom time to time and mixed well. Samples of the contents were testedfor their ability to retard the formation of foam according to theprocedure for the Foam Retard Test.

FOAM RETARD TEST (1) Basis for test The typical amount of heavy-dutycleaning compound (containing about 5% defoaming nonionic surfactant)usually charged to a spraywashing machine is about /2 ounce/gallon ofwater. In brief, this is calculated as 2.84l4.2 g./ gallon for thedetergent composition or 0.142 to 0.710 g./gallon (or 38-190 ppm.) forthe defoaming nonionic surfactant (assuming that none has been lost bydecomposition) in the wash water. The defoaming ability of the defoamingsurfactant is tested in a foammaking machine. Since the foam machineemployed in this test requires about 1.2 gallons water per wash, this isequivalent to using 3.4 to 17 g. of detergent composition.

The amount of food soil selected for this test (i.e. 5 cc. whole egg) issuflicient to cause a very rapid formation of foam, when exposed to theaction of a detergent composition not containing defoaming nonionicsurfactant. For example, a five-inch height of foam will develop within30-60 seconds over a water surface area of 90 sq. inches.

As was previously explained, foaming must be suppressed in order to haveadequate cleaning ability. In this test a drop in water pressure isobserved when the foam height reaches 'two inches. Accordingly, we havearbitrarily set one inch of foam as the maximum amount of foam which canbe tolerated while maintaining elfective cleaning ability.

(2.) Procedure Rinse foam machine well-twise with cold water and twicewith the hot water as it is supplied from a hot water tank.

Drain well.

A heel of 65 0 ml. H O is left in the pump and piping of the system.

Charge detergent composition in quantities of 3 g., 4.5 g., -6 g., or 9g. At the start of each stability test, these amounts of detergentcomposition contain undegnaded defoaming nonionic surfactant in amountssufficient to supply the washwater with concentrations of 3 3, 50, 66 or99 p.p.m. respectively.

Charge [i850 ml. hot 'water (temperature should be about 175" F). (Thetotal water charge is about 4500 ml). T-urn pump on and recycle wateruntil homogeneous. (Temperature of wash water should drop below F. andshould be held above 140 F).

Foam height should be less than Mt inch. Charge 5 ml. of whole egg froma syringe and continue circulation through foam machine. Start stopwatch as soon as egg is charged. Record foam height after 30 seconds and1, 3, 5, 6, 7 and 8 minutes.

(3) Evaluation Readings below one inch after eight minutes is consideredgood retard action and is considered a passing or adequate performance.More than one-inch of foam after eight minutes is a failing retardaction. (Readings of less than inch after eight minutes is excellentretard action).

The following surfactants with and without antioxidant were tested andcompared:

(\A) Reaction pro-duct of one mole n-C H OH with 30 moles ethylene oxideand 50 moles propylene oxide.

(B) Reaction product of one mole didodecylphenol with 45 moles ethyleneoxide and 50 moles propylene oxide.

(C) Reaction product of one mole water with about 45 moles propyleneoxide, about 60 moles ethylene oxide and finally with about 60 molespropylene oxide.

(D) A highly branched amine oxyalky-late.

(E) A methyl ether derivative of .the reaction product of t-octyl-phenoland about 17 moles of ethylene oxide.

The antioxidants employed are as follows:

(1) 1$a11)toquin '(1,2-dihydro-6-ethoxy-2,2,4-trimethyl quin- (i l)Thenothiazine (HI) t-butylphenol-formaldehyde resin (IV) antioxidant2246 2,2'-rnethylene bis-(4-methylo-t-b'utylphenol) (V)dicyolohexylamine (DOHA) The results of 'the Foam Retar-d Test arepresented in Tables Jill and IV. The term Days of Adequate Defoamingrefers to the number of days storage in which a fixed Weight of heavyduty alkaline detergent was able to suppress the foam height below oneinch for 8 minutes.

Results of Foam Retard Test in which the heavy-duty formulation wasstored at about F.

TABLE III AIzlays of e uate Surfactant Anti-oxidant Deio nnng with 9 gor less A 2246/DOHA a 36 A Santoquin 25 A. None i 21 25 25 15 22 C 2125-29 17 a Wt. ratio was 40/60.

Results of Foam Retard Test in which the heavy-duty formulation wasstored at about 110 F.

TABLE IV Da 5 of Ads uate Deioamin Surfactant Antioxidant With 3 g. With4.5 g. or less or less A Santoquin 36 None 21 O. M75 30 [CL Phenoth 30 CNone 11 E Phenothiazine.. 59 E None 29-36 As is quite evident,antioxidants and nonionics will be constantly developed which could beuseful in this invention. It is, therefore, not only impossible toattempt a comprehensive catalogue of such compositions, but to attemptto describe the invention in its broader aspects in terms of specificchemical names of its components used would be too voluminous andunnecessary since one skilled in the art could by following thedescription of the invention herein select a useful composition. Thisinvention lies in the use of suitable antioxidants in conjunction withnonionics and their individual compositions are important only in thesense that their properties can afiect this function. To preciselydefine each specific useful antioxidant, and nonionic in light of thepresent disclosure would merely call for chemical knowledge within theskill of the art in a manner analogous to a mechanical engineer whoprescribes in the construction of a machine the proper materials and theproper dimensions thereof. From the description in this specificationand with the knowledge of a chemist, one will know or deduce withconfidence the applicability of specific antioxidants and nonionics,suitable for this invention by applying them in the compositions setforth herein. In analogy to the case of 'a machine, wherein the use ofcertain materials of construction or dimensions of parts would lead tono practical useful result, various materials will be rejected asinapplicable where others would be operative. One can obviously assumethat no one will wish to employ a useless system nor will be misledbecause it is possible to misapply the teachings of the presentdisclosure to do so. Thus, any antioxidant and nonionic system that canperform the function stated herein can be employed.

Having thus described our invention what we claim as new and desire toobtain by Letters Patent is:

1. A stable alkaline detergent composition for use in machinedishwashing, machine bottlewashing and in general purpose heavy dutycleaners consisting essentially of (1) a mixture of sodium hydroxide,anhydrous sodium metasilicate and sodium carbonate, (2) a defoamingnonionic surfactant selected from the group consisting of (A) thereaction product of one mole n-C H OH with 30 moles ethylene oxide and50 :moles propylene oxide,

(B) the reaction product of one mole didodecylphenol with moles ethyleneoxide and moles propylene oxide,

(C) the reaction product of one mole water with about 45 moles propyleneoxide, about moles ethylene oxide and finally with about 60 mole-spropylene oxide,

(D) a highly branched amine oxyalkylate, and

(E) a methyl ether derivative of the reaction product of t-octylphenoland about 17 moles ethylene oxide, and

(3) an antioxidant selected from the group consisting of (A)1,Z-dihydro-6-ethoxy-2,2,4-trimethyl quinoline,

(B) Phenothiazine,

(C) t-butylphenol-formaldehyde resin,

(D) 2,2methylene bis-(4-methyl 6 t butylphenol),

and

(E) dicyclohexy-lamine,

(2) being present in an amount of 15% by weight of (1), said antioxidantbeing present in an amount suflicient to reduce, inhibit and prevent thedegradation of said nonionic surfactant, whereby said nonionicsurfactant is rendered stable thereby providing a stable alkalinedetergent composition.

References Cited UNITED STATES PATENTS 3,168,478 2/11965 Stefcik 252-1562,976,248 3/1961 Otrhalek 252-'156 3,078,230 2/1963 Cyba 25240'1 OTHERREFERENCES Arthur and Elizabeth Rose, The Condensed Chemical Dictionary,ninth edition, 1961, pp. 231, 391.

MURRAY KATZ, Primary Examiner.

L. D. ROSDOL, Examiner.

B. BETTIS, Assistant Examiner.

